The art today knows fluid-regulating valves which can be shifted by small pneumatic, hydraulic or mechanical forces acting upon a shutter mechanism, thanks to the use of two relatively slidable plates with multiple apertures--usually designed as slits--that are mutually offset in a blocking position and are mutually aligned in an unblocking position. These sensitive valves, therefore, can be used either for direct flow regulation or as pilot valves for the control of associated flow-regulating valves. The precise design of their operating elements, however, makes them susceptible to various factors which may impair their function, among them possible blockages of fluid passages and inaccurate guidance of connecting members. When, for example, the valve body or housing includes a compartment bounded by a membrane or other resiliently biased member displaceable by fluid under pressure, that compartment ought to have a calibrated bleeding hole whose cross-sectional area determines the pressure required for opening or closing the valve. Such a bleeding hole is usually of rather small diameter and is therefore liable to become clogged by impurities or, if the controlling fluid is a hardenable liquid, by a residue of that liquid when the influx thereof has ceased.
In the case of a pilot valve controlled by a float measuring the level of a liquid, e.g. in a pool intermittently fed with fresh liquid by way of that valve, the movement of that float is nonlinear when its support consists of a lever fulcrumed on the valve housing. The translation of the swing of that lever into a linear motion of a sliding shutter also creates problems which heretofore have made it difficult to utilize valves of the aforementioned sensitive type for this purpose.